Process of producing a foundry core composition

ABSTRACT

A FOUNDRY CORE COMPOSITION WHICH IS THE PRODUCT OF THE PROCESS WHICH COMPRISES: (A) FORMING A MONOMERIC BINDER MIXTURE OF SPECIFIED AMOUNTS OF AQUEOUS UREAFORMALDEHYDE MIXTURE, FURFURYL ALCOHOL, AND A SILIANE COUPLING AGENT OF THE GENERAL FORMULA:   X-R&#39;&#39;SI-(OR&#34;)3   WHEREIN R&#39;&#39; IS A SHORT CHAIN ALKYLENE RADIAL, R&#34; IS ARYL, ALKYL, SUBSTITUTED ARYL, OR FURFURYL, AND X IS AMINO, MERCAPTO, EPOXY, OR GLYCIDOXY, (B) FORMING A MIXTURE OF SPECIFIED AMOUNTS OF SAND AND ACIDIC CATALYST, AND (C) ADMIXING SPECIFIED AMOUNTS OF THE MONOMERIC BINDER WITH SPECIFIED AMOUNTS OF THE SAND-ACIDIC CATALYST MIXTURE.

United States Patent 3,734,936 PROCESS OF PRODUCING A FOUNDRY CORE COMPOSITION Lloyd H. Brown, Crystal Lake, and Daniel S. P. Eftax,

Barrington, Ill., assignors to The Quaker Oats Company, Chicago, Ill. No Drawing. Filed Feb. 3, 1971, Ser. No. 112,485 Int. Cl. C08g 51/04 US. Cl. 260-395 B 14 Claims ABSTRACT OF THE DISCLOSURE A foundry core composition which is the product of the process which comprises: (a) forming a monomeric binder mixture of specified amounts of aqueous ureaformaldehyde mixture; furfuryl alcohol; and a silane coupling agent of the general formula:

XR-Si-(OR) wherein R is a short chain alkylene radical; R is ary alkyl, substituted aryl, or furfuryl; and X is amino, mercapto, epoxy, or glycidoxy; (b) forming a mixture of specified amounts of sand and acidic catalyst; and (c) admixing specified amounts of the monomeric binder with specified amounts of the sand-acidic catalyst mixture.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to foundry cores.

Description of the prior art A foundry core may be defined as that part of shaped sand and binding material that aids in forming an internal part of metal casting. There are several requirements for a foundry core. It must usually cure rapidly; it must resist the washing and burning action of a stream of hot metal; it must admit of the free escape of gases; it must impart its internal contour to the metal casting; it must have sufficient tensile strength so that it is not ruptured while being handled or worked; and finally it must shake out readily after the metal casting has hardened.

To satisfy some of these requirements the foundry art has long employed sand along with a suitable binder. A

binder may be defined as that part of the foundry core composition which causes adhesion among the sand particles. In the following description the term binder will include all organic ingredients of the foundry core composition.

Various binders have been used by the foundry industry. One of the oldest known binders is the cereal-core oil binder. The main disadvantage of this system is the long curing time required. Today with the use of highspeed automatic equipment a rapid curing binder is very desirable.

Another type of core binder is made from phenolic resins. Because of the high cost of such resins, the binder is used to merely bond a shell instead of acting as a binder throughout the core. The use of phenolic resin type binders results in foundry cores that have a tendency to resist shakeout after the metal casting has hardened, particularly when casting low-melting non-ferrous alloys. Also the curing time required and the tensile strengths of the resulting foundry cores could be improved.

A third type of core binder is the urea-formaldehyde cereal binder. This system requires suificient water to be present in order that the foundry core will have sufiicient green or wet strength to retain its shape until it is placed in an oven. The presence of water in the required quantities increases the curing time. In addition this binder produces a core that collapses too readily on contact with high-temperature melting metals, such as grey iron. Another problem with the core produced by this binder is the lack of humidity resistance. Lack of such resistance causes the core to lose strength upon exposure to an atmosphere with high humidity.

Still another type of core binder that is familiar to the prior art is one made from furfuryl alcohol and ureaformaldehyde such as is described in US. Pat. No. 3,168,489. These binders, like the urea-formaldehyde cereal binders, are high in formaldehyde content often having as much urea-formaldehyde as furfuryl alcohol or cereal. These binders suffer from the obvious difiiculty encountered by personnel when a large amount of free formaldehyde is present. There is, therefore, a need to produce a good binder system that is not substantially high in formaldehyde content.

This invention provides a new and novel core composition which overcomes many of the problems and difficulties associated with the prior art.

SUMMARY OF THE INVENTION It is an object of this invention to provide a foundry core that has an improved tensile strength.

Another object of this invention is to provide a core composition that cures rapidly so that it may be used with high-speed automatic machinery.

Still another object of this invention is to provide a foundry core which can withstand the heat from a high melting point metal and yet can be readily shaken out after the metal casting has hardened.

A further object of this invention is to provide a foundry core from materials that are relatively inexpensive as compared to many presently used materials.

A still further object of this invention is to provide a foundry core that does not lose strength in a high humidity atmosphere.

The objects of this invention are accomplished by a foundry core composition which is the product of the process comprising the steps of:

(a) Forming a monomeric binder mixture of from 2 percent to 10 percent by weight of aqueous urea-formaldehyde mixture; from 97.9875 percent to 89.5 percent by weight furfuryl alcohol, said aqueous urea-formaldehyde mixture containing from about 5 percent to about 25 percent by weight water; and from 0.0125 percent to 0.5 percent by weight of a silane coupling agent of the general formula:

X-R'--Si( OR" 3 wherein R is a short chain alkylene having between about 3 and 6 carbon atoms; R is aryl, alkyl, substituted aryl, or heteroalkyl; and X is amino, mercapto, epoxy, or glycidoxy;

(b) Forming a mixture of sand and acidic catalyst, said sand and said acidic mtalyst being mixed in a proportion such that when from /2 percent to 5 percent by weight monomeric binder is mixed with from 99.5 percent to percent by weight of the sand-acidic catalyst mixture, the acidic catalyst is present in an amount of from 5 percent to 50 percent by weight of the monomeric binder; and

(c) Admixing from /2 percent to 5 perecnt by weight of the monomeric binder with from 99.5 percent to 95 percent by weight of the sand-acidic catalyst mixture.

More particularly, the objects of this invention are accomplished by a foundry core composition which is the product of the process comprising the steps of (a) Forming a monomeric binder mixture of from 2 percent to 10 percent by weight of aqueous urea-formaldehyde mixture; from 97.9875 percent to 89.5 percent by weight furfuryl alcohol, said aqueous urea-formaldehyde mixture containing from about 5 percent to about 25 percent by weight water; and from 0.0125 percent to 0.5 percent by weight of a silane coupling agent or the general formula:

XR'--Si(OR) wherein R is a short chain alkylene having between about 3 and 6 carbon atoms; R" is aryl, alkyl, substituted aryl, or heteroalkyl; and X is amino, mercapto, epoxy, or glycidoxy;

(b) Forming a mixture of from 3700 to 3979 parts by weight sand and from 1 to 100 parts by weight acidic catalyst; and

(c) Admixing from /2 percent to 5 percent by weight of the monomeric binder with from 95 percent to 99.5 percent by weight of the sand-acidic catalyst mixture.

This invention includes the use of from 2 percent to percent by weight of aqueous urea-formaldehyde mixture in forming a monomeric binder.

Aqueous urea-formaldehyde mixtures are sold in commerce. One example is U.F. Concentrate85 sold by the Nitrogen Division of Allied Chemical & Dye Corporation, South Point, Ohio. Another aqueous urea-formaldehyde mixture is made by E. I. du Pont de Nemours and Company, Wilmington, Delaware, and is marketed as Urea-Formaldehyde 2560. Other examples of aqueous urea-formaldehyde mixtures are Sta-Form 60 by Georgia-Pacific Company, Portland, Oregon, UF85 and UP-78 by Borden Chemical Division, Borden, Inc., New York, N.Y., Agrimine by Reichhold Chemical, Inc., White Plains, New York, Formourea 60 by Montecatini Edison of Italy, and Formol 55 by Badische Anilin- & Soda-Fabrik of Germany. The formaldehyde, urea, and equilibrium reaction products thereof, present in aqueous urea-formaldehyde mixtures are believed to exist in equilibria as follows:

NH CONH -l-HCOiNH CONHCH OH NH CONHCH OH+HCHO:HOCH NHCONHCH OH HOCH NHCONHCH OH +HCHO :HOCH NHCON (CH OH) 2 HOCH NHCON (CH OH +HCHO 7- (HOCH NCON CH OH) 2 The above equilibria illustrates what is meant by the phrase a non-polymerized aqueous mixture of formaldehyde, urea, and equilibrium reaction products thereof. Those urea molecules in the equilibria shown above that have more than one methylol radical attached are sometimes referred to as polymethylol ureas. There is difiiculty encountered in distinguishing between the different polymethylol ureas in the aqueous urea-formaldehyde mixtures. For this reason the composition of the aqueous urea-formaldehyde solution is reported in terms of the weight percent urea and formaldehyde. A typical analysis of Allied Chemicals aqueous urea-formaldehyde mixture (U.F. Concentrate-85) shows 59 percent by weight formaldehyde, 26 perecnt by weight urea, and about percent by weight water.

The aqueous urea-formaldehyde mixture hereinbefore described may contain from about 5 perecnt to about perecnt by weight water.

It is to be noted that the aqueous urea-formaldehyde mixture as described herein can be present in an amount of from 2 percent to 10 percent by weight. At the upper concentration of aqueous urea-formaldehyde, i.e. 10 percent and above, the concentration of free formaldehyde begins to create a formaldehyde odor that makes the binder unacceptable due to personnel exposure. This invention, therefore, makes use of an aqueous urea-formaldehyde mixtur without presenting the serious problems normally associated with the use of formaldehyde.

While we prefer to use gamma-aminopropyltriethoxysilane in the monomeric binder of this invention, other suitable silane coupling agents include the following for example:

gamma-mercaptopropyltrimethoxysilane; N-beta- (aminoethyl -gamma-aminopropyltrimethoxysilane; beta- 3,4-epoxycyclohexyl) ethyltrimethoxysilane; gamma-glycidoxypropyltrimethoxysilane; gamma-aminopropyltriphenoxysilane; gamma-aminopropyltribenzyloxysilane; gamma-aminopropyltrifurfuroxysilane; gamma-aminopropyltri (o-chlorophenoxy) silane; gamma-aminopropyltri (p-chlorophenoxy) silane; and gamma-aminopropyltri (tetrahydrofurfuroxy) silane.

The monomeric binder mixture of this invention also includes from 89.5 percent to 97.9875 percent by weight furfuryl alcohol. It is to be emphasized that the furfuryl alcohol must be monomeric as opposed to polymerized furfuryl alcohol, furfuryl alcohol resins, or condensed furfuryl alcohol. It must also be emphasized that the binder mixture of this invention must also be monomeric and not contain substantial quantities of polymerized ingredients.

This invention includes forming a mixture of sand and acidic catalyst to be mixed with the monomeric binder mixture. The acidic catalyst must be mixed with the sand in a proportion such that when from /2 percent to 5 percent by weight monomeric binder is mixed with from 99.5 percent to 95 percent by weight of the sand-acidic catalyst mixture, the acidic catalyst is present in an amount of from 5 percent to 50 percent by weight of the monomeric binder. Generally this can be accomplished by mixing from 3700 to 3979 parts by weight sand with from 1 to 100 parts by weight acidic catalyst. The amount of an acidic catalyst employed in the sandcatalyst mixture will vary within the stated range depending upon the type of sand used and also the curing properties that are desired. Sands with a high clay content may have a high acid demand and require more acid catalyst. Generally any acidic catalyst may be employed, e.g. toluene sulfonic acid, phosphoric acid, ammonium chloride, ammonium trichloroacetate, ammonium phosphate, ammonium sulfate and ammonium nitrate. A solution of percent toluene sulfonic acid in water or an percent solution of phosphoric acid in water are particularly well adapted for use as a catalyst in this invention.

In practicing this invention the monomeric binder mixture is first prepared by admixing the components as hereinbefore described. Also the sand and acidic catalyst are prepared in the proportions hereinbefore described. Next the monomeric binder is mixed with the sand-acidic catalyst mixture. In this mixture the monomeric binder constitutes from /2 percent to 5 percent by Weight of the mixture while the sand-acidic catalyst mixture constitutes the remaining 99.5 percent to percent by weight of the mixture.

DESCRIPTION OF THE PREFERRED EMBODIMENTS This invention will be further illustrated, but is not limited by the following examples. Examples 3, 5, 7, and 9 may be taken to be preferred embodiments of this invention.

In the examples a comparison of certain properties of the foundry cores is made to demonstrate the advance in the art accomplished by this invention. When tensile strength was used as a method of comparison of the foundry cores, this test was conducted according to standards described in Section 13 of the Foundry Sand Handbook, seventh edition, copyright 1963, by the American Foundry Society, Inc., Des Plaines, Illinois. When scratch hardness was used as a method of comparison of the foundry cores, this test was conducted according to Section 16 of the same publication.

The urea-formaldehyde mixture used in each of the examples is a urea-formaldehyde 85 type concentrate.

In those examples where life of the core is used as a method of comparison, the life may be taken to be the number of minutes in which it takes greater than six compressions on a sample to achieve the same compressed length as three compressions of the sample would originally achieve.

EXAMPLE 1 A quantity of silica sand was weighed and set aside. Next a quantity of furfuryl alcohol binder equal to 2 percent by weight of the silica sand was weighed and set aside. Next a 70 percent solution of toluene sulfonic acid in water equal to 17 percent by weight of the furfuryl alcohol binder was mixed with the silica sand. After the sand and acid were thoroughly mixed, the furfuryl alcohol binder was then thoroughly mixed in. Cores were made for this material, allowed to cure at ambient temperatures from 2 to 3 hours, then placed at 23 percent relative humidity overnight, a core made from this mixture was found to have a tensile strength of 276 p.s.i. and a scrach hardness of 92. Afer overnight at 93 percent relative humidity a foundry core prepared from this composition had a tensile strength of 72 p.s.i. and a scratch hardness of 83. The life of a core prepared from this mixture was 11 minutes. This example is not in accordance with this invention but is used merely to provide a comparison of a core made with a furfuryl alcohol binder.

EXAMPLE 2 Example 1 was repeated with the exception that furfuryl alcohol binder was replaced by a binder consisting of 95 percent by weight furfuryl alcohol and 5 percent by weight of aqueous urea-formaldehyde. Also, the amount of toluene sulfonic acid was increased to 20 percent by weight of the binder. Cores were made from this mixture, allowed to cure at ambient temperatures for 2 to 3 hours, then placed at 93 percent relative humidity overnight, the tensile strength of one of these foundry cores was 81 p.s.i. and the scratch hardness was 83. The life of this core was 15 minutes. This example is also not in accordance with this invention, but is used as a comparison of a core made from a binder containing only furfuryl alcohol and aqueous urea-formaldehyde.

EXAMPLE 3 A quantity of silica sand was weighed and set aside. Next a monomeric binder was prepared consisting of about 97.9 percent furfuryl alcohol, about 2 percent aqueous urea-formaldehyde and 0.1 percent gamma-aminopropyltriethoxysilane. An amount of this binder equal to 2 percent by weight of the silica sand was then weighed and set aside. Next, a 70 percent solution of toluene sulfonic acid in water equal to 17 percent by weight of the monomeric binder was thoroughly mixed with this silica sand. The sand-acid mixture was then thoroughly mixed with the monomeric binder. Cores were made from this material, allowed to cure at ambient temperatures for 2 to 3 hours, then placed at 93 percent relative humidity overnight, one of these foundry cores was found 0 have a tensile strength of 305 p.s.i., a scratch hardness of 92, and a life of 17 minutes. This example is in accordance with this invention and illustrates one preferred embodiment of this invention.

EXAMPLE 4 Example 2 was repeated with the exception that the silica sand was replaced by lake sand and the binder consisted of 92 percent furfuryl alcohol and 8 percent aqueous urea-formaldehyde. Also, the amount of catalyst was increased to 25 percent by weight of the binder. 'A foundry core prepared from this mixture, allowed to cure at ambient temperatures for 2 to 3 hours, then placed at 93 percent relative humidity overnight, found to have a tensile strength of 161 p.s.i. This example is not in accordance with this invention, but is used merely as an example of a binder which does not contain the gammaaminopropyltriethoxysilane.

EXAMPLE 5 Example 4 was repeated with the exception that 0.1 percent of the furfuryl alcohol was replaced with 0.1 percent gamma-aminopropyltriethoxysilane. After overnight at 93 percent relative humidity, the tensile strength of a foundry core prepared from this mixture was 275 p.s.i.

EXAMPLE 6 Example 4 was repeated except the lake sand Was replaced by silica sand and the toluene sulfonic acid was replaced by an percent solution of phosphoric acid in water. After overnight at a relatively humidity at 93 percent, a foundry core produced from this mixture was found to have a tensile strength of 5 6 p.s.i. After overnight at a relative humidity of between 20 percent and 30 percent, a foundry core produced from this mixture was found to have a tensile strength of 373 p.s.i. Like Example 4, this example is not an embodiment of this invention, but is used as a means of comparison of a foundry core prepared with a different acid catalyst.

EXAMPLE 7 Example 6 was repeated except 0.4 percent of the furfuryl alcohol was replaced by 0.4 percent gamma-aminopropyltriethoxysilane. After overnight at 93 percent relative humidity, a foundry core prepared from this mixture had a tensile strength of 399 p.s.i. After overnight at a relative humidity controlled at between 20 percent and 30 percent, a foundry core produced by this mixture was found to have a tensile strength of 582 p.s.i. This example is in accordance with this invention and may be taken to be a preferred embodiment of this invention.

EXAMPLE 8 Example 6 was repeated with the exception that the acidic catalyst was increased to 30 percent by weight of the binder. After overnight at 93 percent relative humidity, the tensile strength of a foundry core prepared from this mixture was 78 p.s.i. After overnight at 20 percent relative humidity, a foundry core prepared from this mixture had a tensile strength of 417 p.s.i. and a life of 14 minutes. This example is not in accordance with this invention but is used to provide a means of comparison of a foundry core prepared from a higher level of acidic catalyst.

EXAMPLE 9 Example 8 was repeated with the exception that 0.1 percent of the furfuryl alcohol was replaced by 0.1 percent :gamma-aminopropyltriethoxysilane. After overnight at 93 percent relative humidity, a foundry core produced from this mixture had a tensile strength of 217 psi. After overnight at a relative humidity of 20 percent, a foundry core prepared from this mixture had a tensile strength of 467 p.s.i. and a life of 27 minutes. This example is in accordance with this invention and may be taken to be a preferred embodiment of this invention.

EXAMPLE 10 A monomeric binder mixture using various parts by weight of furfuryl alcohols, urea, formaldehyde, and gamma-aminopropyltriethoxysilane. An amount of 85 percent phosphoric acid in water equal to 25 percent by Weight of the monomeric binder was then mixed with a quantity of Wedron silica sand. Next 2 percent by weight of the monomeric binder was mixed with the sand catalyst mixture. Foundry cores were prepared from the mixture, allowed to cure at ambient temperatures for 2 to 3 hours, then placed at two different relative humidity ranges overnight. The results are shown in Table I.

TABLE I Monomeric binder system (parts by weight) Tensile strength after overnight Aqueous Gammacure (p.s.i.)

Furureaaminopropyl- Free Test t'uryl ormaldetrlethoxy- 26-34% 93% CHzO N 0. alcohol hyde silane RH. R .11. percent EXAMPLE 11 Test is not 111 accordance with this invention but Monomeric binder mixtures using 92 parts by weight of furfuryl alcohol, 8 parts by weight of aqueous ureaformaldehyde, and 0.1 part by weight of various silane coupling agents were prepared. The type of silane coupling agent used in each test is given in Table II. An amount of 85 percent phosphoric acid in water equal to percent by weight of the monomeric binder was then mixed with a quantity of Wedron silica sand. Next 2 percent by weight of the monomeric binder was mixed with the sand-catalyst mixture. Foundry cores were prepared from the mixture, allowed to cure at ambient temperature for 2 to 3 hours, then placed at two difierent relative humidity ranges overnight. The results are shown in Table II.

Test 14 is not in accordance with this invention but was prepared as in example of a binder which does not contain a silane coupling agent.

EXAMPLE 12 Other monomeric binder mixtures using 92 parts by weight of furfuryl alcohol, 8 parts by weight of aqueous urea-formaldehyde, and 0.1 part by weight of various silane coupling agents were prepared. The type of silane coupling agent used in each test is given in Table III. An amount of 85% phosphoric acid in water equal to percent by weight of the monomeric binder was then mixed with a quantity of Wedron silca sand. Next 2 percent by weight of the monomeric binder was mixed with the sand-catalyst mixture. Foundry cores were prepared from the mixture, allowed to cure at ambient conditions for 2 to 3 hours, then placed at two dilferent relative humidity ranges overnight. The results are shown in Table III.

was prepared as an example of a binder which does not contain a silane coupling agent.

The above examples clearly demonstrate the accomplishment of this invention. In Examples 1 and 2, binders consisting of fnrfuryl alcohol and furfuryl alcohol-aqueous urea-formaldehyde were found to have tensile strengths 72 p.s.i. and 81 p.s.i. respectively and lives of 11 minutes and 15 minutes respectively. When 0.1 percent gammaaminopropyltriethoxysilane was added to the binder, as is illustrated in Example 3, the tensile strength increased dramatically to 305 p.s.i., and the life increased to 17 minutes. The tremendous increase in tensile strength from about p.s.i. to over 300 p.s.i. clearly demonstrates the exceptional achievement of this invention.

A further illustration of the improvement of this invention is illustrated by Examples 4 and 5. Example 5 is the same as Example 4 with the exception that 0.1 percent gamma-aminopropylthiethoxysilane has been added to the monomeric binder. Again, the tensile strength clearly demonstrates the advancement provided by this invention. Without the silane, the tensile strength was 161 p.s.i. With the silane, the tensile strength increased to 275 p.s.i., a 71 percent increase in tensile strength.

Examples 6 and 7 again illustrate the tremendous improvement accomplished by this invention when a different acidic catalyst is used and when higher amounts of silane are used. These examples are the same with the exception that the monomeric binder of Example 7 contains 0.4 percent gamma-aminopropyltriethoxysilane. At difierent humidity levels, the tensile strength was shown to be increased by the silane from 373 p.s.i. to 582 p.s.i. at lower humidity level and from 56 p.s.i. to 399 p.s.i. at higher humidity of cure level. The latter increase of over 600 percent is a further illustration of the significant achievement of this invention.

Examples 8 and 9 are still further examples of the improvement achieved by this invention. These examples are the same with the exception that Example 9 includes 0.1 percent gamma-aminopropyltriethoxysilane in the monomeric binder. In these examples the tensile strength was shown to be increased by the silane (at a high humidity cure) to 217 p.s.i. from 78 p.s.i. The life of the core was to almost doubled in increasing from 14 minutes to 27 minutes.

Example 10 gives further evidence of the significant advance made by this invention. In each of the tests of this example, it is shown that the new and unique combination of this invention provides a substantial improvement over known prior foundry practices. The improvement produced by the combination of high furfuryl alcohol content and moderate to small amounts of aqueous urea-formaldehyde in combination with gamma-aminopropyltriethoxysilane is clearly demonstrated. Free formaldehyde levels are given to illustrate that above about 10 percent aqueous urea-formaldehyde content the free formaldehyde is no longer insignificant and the ureaformaldehyde content must therefore be limited.

A still further illustration of the improvement of this invention is illustrated by Examples 11 and 12. In both of these examples, the tensile strength clearly demonstrated the advancement provided by this invention. Without the silane in both examples, the tensile strength is less than with the silane.

The above examples clearly demonstrate that this invention has significantly advanced the foundry art.

Among the many advantages that are achieved by this invention is that the furfuryl alcohol monomer is resinified in situ in the sand rather than resinified prior to its introduction into the sand. This one step procedure of accomplishing two steps at one time has an obvious commercial advantage.

Having fully described this new and novel invention, we claim:

1. A foundry core composition comprising:

(a) from /2 percent to 5 percent by weight of a monomeric binder mixture of from 2 percent to percent by weight of aqueous urea-formaldehyde mixture; from 97.9875 percent to 89.5 percent by weight furfuryl alcohol, said aqueous urea-formaldehyde mixture containing from about 5 percent to about percent by weight water; and from 0.0125 percent to 0.5 percent by weight of a silane coupling agent of the general formula:

wherein R is a short chain alkylene radical having between 3 and 6 carbon atoms; R" is a radical selected from the group consisting of aryl, substituted aryl, alkyl, and furfuryl; and X is a reactive member selected from the group consisting of amino, mercapto, epoxy, and glycidoxy; and

(b) from 95 percent to 99.5 percent by weight of a mixture of sand and acidic catalyst, said sand and said acidic catalyst being mixed in a proportion such that, when the monomeric binder and sand-acidic catalyst mixture is mixed, the acidic catalyst is present in an amount of from 5 percent to 50 percent by weight of the monomeric binder.

2. The foundry core composition of claim 1 wherein the silane coupling agent is gamma-aminopropyln'iethoxysilane.

3. The foundry core composition of claim 1 wherein the silane coupling agent is gamma-mercaptopropyltrimethoxysilane.

4. Thte foundry core composition of claim 1 wherein the silane coupling agent is N-beta-(aminoethyl)-gammaaminopropyltrimethoxysilane.

5. The foundry core composition of claim 1 wherein 50 MORRIS LIEB 7. The foundry core composition of claim 1 wherein the silane coupling agent is gammaaminopropyltriphenoxysilane.

8. The foundry core composition of claim 1 wherein the silane coupling agent is gamma-aminopropyltribenzyloxysilane.

9. The foundry core composition of claim 1 wherein the silane coupling agent is gamma-aminopropyltrifurfuroxysilane.

10. The foundry core composition of claim 1 wherein the silane coupling agent is gamma-aminopropyltri(ochlorophenoxy silane.

11. The foundry core composition of claim 1 wherein the silane coupling agent is gamma-aminopropyltri(pchlorophenoxy)silane.

12. The foundry core composition of claim 1 wherein the silane coupling agent is gamma-aminopropyltri(tetrahydrofurfuroxy) silane.

13. The foundry core composition as in claim 1 in which said acidic catalyst is toluene sulfonic acid.

14. A foundry core composition comprising:

(a) from V: percent to 5 percent by weight of a monomeric binder mixture of from 2 percent to 10 percent by weight of aqueous urea-formaldehyde mixture; and from 97.9875 percent to 89.5 percent by weight furfuryl alcohol, said aqueous urea-formaldehyde mixture containing from about 5 percent to about 25 percent by weight water; and from 0.0125 percent to 0.5 percent by weight of a silane coupling agent of the general formula:

wherein R is a short chain alkylene radical having between about 2 to 6 carbon atoms; R" is a radical selected from the group consisting of aryl, substituted aryl, alkyl, and furfuryl; and X is a reactive member selected from the group consisting of amino, mercapto, epoxy, and glycidoxy; and

(b) from percent to 99.5 percent by weight of a mixture of from 3700 to 3979 parts by weight sand and from 1 to parts by weight acidic catalyst.

References Cited UNITED STATES PATENTS 3,168,489 2/1965 Brown et a1 164-43 X 3,538,035 11/1970 Cleek et a1 164-43 X 3,403,721 10/1968 Robins et a1. 164-43 3,290,165 12/1966 Iannicelli 260-415 R X 3,471,429 10/ 1969 Hayford 260-294 R MAN, Primary Examiner S. M. PERSON, Assistant Examiner US. Cl. X.R.

5 164-43; 26029.4 R, 37 R, DIG. 40 

